The invention relates to a system for cooling and heating, having a first heat exchanger for outputting heat to and extracting it from a heat reservoir; a second heat exchanger for extracting heat from and outputting it into a space to be cooled or heated; a compressor; an expansion device; and means for switchover between a cooling mode and a heating mode. The invention also relates to a method for switching over between a cooling mode and a heating mode by means of a system having a first heat exchanger for outputting heat into and extracting it from a heat reservoir, a second heat exchanger for extracting heat from and outputting it into a space to be cooled or heated, a compressor, an expansion device, and means for switchover between a cooling mode and a heating mode.
Systems and methods of this generic type are known, particularly for cooling and heating internal compartments of motor vehicles. Cooling with such systems and methods using an air conditioner built into a motor vehicle has already been known for a long time. Increasingly, however, heating with such systems is also gaining in importance. The reason for this is not least the development of engines with optimized fuel consumption, since in these engines not enough heat is output to the coolant to heat the vehicle comfortably in low-load operation at low temperatures. This is true particularly for direct-injection Diesel engines, which already fundamentally have additional heaters to assure comfort at low temperatures. Motor vehicles with direct gasoline injection will in future also have to be equipped with additional heaters, if a comfortable interior temperature is to be maintained.
Most vehicles in the top price class and increasingly the middle price class as well have an air conditioner as standard equipment. At low ambient temperatures, the components of such an air conditioner can be utilized as a heat pump by reversing the heat circulation. Such a heat pump is distinguished by low energy consumption and spontaneous response performance at high heating capacity. With a view to safety, window de-icing, and passenger comfort, this is an appropriate concept for designing additional heaters for the future.
In FIGS. 5 and 6, two air conditioner circuits are shown; in FIG. 5, a conventional cooling mode is illustrated, while in FIG. 6 a heating mode is shown, with the components additionally required for the heating mode.
In FIG. 5, an air conditioner circuit is shown schematically. A first medium enters a first heat exchanger 110 and flows through a loop 160. The medium outputs heat to the ambient air 162 and thus cools itself. From the heat exchanger 110, a cooled medium emerges. This cooled medium is now passed through an internal heat exchanger 128, whose function will be explained hereinafter. After the medium has emerged from the internal heat exchanger 128, it enters an expansion device 120. The medium cools down sharply by expansion and is then delivered to a second heat exchanger 114. In this heat exchanger 114, the cold medium can cool down warm ambient air or circulating air and can be made available in the form of cold air 164 to a space to be cooled, such as the vehicle interior. In this process, the formation of condensate 166 occurs. The medium, now re-heated and evaporated because of the heat exchange in the heat exchanger 114, emerges from the heat exchanger 114 and then flows through the internal heat exchanger 128 again. After emerging from the internal heat exchanger 128, the medium enters a compressor 118, where by compression it is put at a higher pressure and heated. A heated medium is thus again available, which can enter the first heat exchanger 110 for the purpose of heat exchange. The loop is closed.
The internal heat exchanger 128 serves to increase the capacity of the loop. Thus the medium before entering the expansion device 120 is cooled by the returning medium that has emerged from the second heat exchanger 114, while the returning medium is heated by reflux. As a result of this heat exchange, the proportion of liquid in the fluid upon leaving the expansion device 120 is increased. This increases the efficiency in the loop.
In FIG. 6, a loop is shown which in comparison with FIG. 5 is equipped with additional components. These components are required in order to use the loop for heating a space. Once again, the loop will be described beginning at the inflow of the medium into the first heat exchanger 110. Cold medium enters the heat exchanger 110. In the heat exchanger, the cold medium is heated and evaporated by interaction with the ambient air 162, while the ambient air is cooled down. Depending on the temperature, the formation of condensate or ice 168 can occur. After the medium flows out of the first heat exchanger, it flows via a first valve 170 into the internal heat exchanger 128: After the medium emerges from the internal heat exchanger 128, it flows into the compressor 118, where it is compressed and heated. Once the medium has left the compressor, it flows via a second valve 172 into the second heat exchanger. There, the heated medium can heat cold ambient air or cold circulating air and thus can be available as useful heat 174 to a space to be heated. The medium emerges in the cooled state from the second heat exchanger 114 and then flows into a third valve 176. This third valve 176 directs the flow of the medium to a fourth valve 178, where once again the medium is directed such that it enters the internal heat exchanger 128. After emerging from the internal heat exchanger 128, the medium enters the expansion device 120, where it is cooled by expansion, and then via a valve 178 it is directed into the first heat exchanger again. The loop of the medium is closed.
Once again, the internal heat exchanger 128 serves to increase the capacity. First, the heated medium, which is to be further heated in the compressor 118, is heated in the internal heat exchanger 128 by the returning medium, which in turn flows into the internal heat exchanger from the second heat exchanger 114. Second, this returning medium, before cooling down by expansion in the expansion device 120, is cooled down by the medium entering the heat exchanger, which medium has emerged from the first heat exchanger 110.
It can be seen that to achieve a system which makes both a cooling mode and a heating mode possible, additional components are required. These are in particular the valves 170, 172, 176 and 178, which by means of suitable switchover can form either a heating loop or a cooling loop. Besides the valves 170, 172, 176 and 178, other additional components are necessary, such as supplementary lines, which means a further increase in weight and further complication and expense. Also, because of the greater number of requisite lines and above all connections, the vulnerability to malfunction and in particular the incidence of leaks are increased.